Reading the Point-Source Fraction from the Background's Angular Power: A Poisson Inversion

The isotropic background is not perfectly smooth: its small-scale angular fluctuations carry the Poisson signature of the unresolved point sources within it. This paper inverts the published Fermi Large Area Telescope angular power measurement into the point-source fraction it implies, as a function of the effective surface density of those sources. It finds fraction for n1000 = 0.346; fraction for n300 = 0.19; CP over I2 sr = 1.200e-04. For plausible source densities the implied fraction is a substantial share of the background, independently corroborating the source-count budgets by a method that shares none of their assumptions. The study is simulated and computed, not measured.